My apologies, girlfriend. And she IS human I take it. The amount of pee a healthy human person is expected to produce is pretty well standard. That's why the WHO is able to produce their reports on the matter. The math, therefore, does apply to everyone because it's applying the same physics that most every human being adheres to.
And based on what you're saying, it sounds like she isn't using the diaper fully after all. She is only releasing small amounts which the diaper can handle- not what her kidneys are producing and certainly not a full bladder. And after 4-5 hours she needs to pee more, enough to stop slightly using the diaper and use the toilet.
Is that about right? Because if so, then she isn't fully using the diaper as we have already guessed. And look, it really doesn't matter if she does or not, I really don't care. Just don't make it sound like a baby diaper can handle the full urine output of an adult. Basic physics dictates they can't, not over the time period your describing.